Flew RV7 #72847 for the first time a week ago last Tuesday and some since then. It has a heavy aileron problem not a heavy wing problem. The ailerons are straight it flight and so is the stick but if you let go of the stick it SNAPS to the left stop. So would you classify that as a wing heavy problem or a heavy aileron problem? How would you suggest it be fixed? The right aileron outboard hinge is about 1/6 inch higher that the inboard hinge. The flaps are straight and adjusting them doesn't change it. Is this one of those things wher the aileron needs to be squeezed. They both look to be symetrical with each other.
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Aileron Heavy?
- Thread starter hudgin
- Start date
When you say that it snaps to the left, I assume you mean on the ground. It would be an interesting ride if it did that in flight!
The ailerons should not do this. Which aileron trim system do you have? Are you sure that you don't have a large amount of left aileron trim dialed in? That would be one way to cause the stick to snap to the left.
Just a thought.
The ailerons should not do this. Which aileron trim system do you have? Are you sure that you don't have a large amount of left aileron trim dialed in? That would be one way to cause the stick to snap to the left.
Just a thought.
I think you're on the right track with the hinge height discrepancy. I heard from another builder that he had a similar problem, though I don't know if it was as extreme. I remember him saying how surprised he was that such a small misalignment could cause such a big problem. If memory serves me, he was able to elongate the bracket holes to correct the alignment, which solved his problem.
Seems like a call to Van's on Monday for their opinion wouldn't hurt either...
Good luck and be safe!
Seems like a call to Van's on Monday for their opinion wouldn't hurt either...
Good luck and be safe!
Steve Sampson
Well Known Member
Hudgin, what you describe is the classic heavy wing. There is a bit somewhere on VANS website regarding how to fix it (see below), but let me explain briefly.
First if the ailerons are out of line in some way you want to fix that.
Before you investigate the ailerons though, make sure the ball is in the center, because if you are flying yawed, the ailerons will have differential lift.
Assuming that is all resolved and you still have the problem the issue works like this. With the stick in the middle the ailerons are all ligned up and she flies correctly, however if you let go she roles left or right. I forget which way for you, but whatever.
The issue is this. One aileron is developing more lift than the other. While this is so slight it does not roll the aircraft while you hold the stick, it is enough to lift an aileron if you let go. The aircraft will then role towards the lifting aileron and will continue to roll since it will remain up.
The common solution is then to squeeze the aileron of the non-heavy wing. This causes its aileron to produce less lift. Its complicated as to why but if you want to understand, and like maths, read up about the Kutta Condition.
I recently had all these problems and currently have a bit of wood to bias first the rudder and then half a coffee stirer stick to bias the aileron. I havnt done the squeeze yet. If you want to see pictures go here. About half way down. You will find links to VANS article and an explanation of the Kutta condition.
First if the ailerons are out of line in some way you want to fix that.
Before you investigate the ailerons though, make sure the ball is in the center, because if you are flying yawed, the ailerons will have differential lift.
Assuming that is all resolved and you still have the problem the issue works like this. With the stick in the middle the ailerons are all ligned up and she flies correctly, however if you let go she roles left or right. I forget which way for you, but whatever.
The issue is this. One aileron is developing more lift than the other. While this is so slight it does not roll the aircraft while you hold the stick, it is enough to lift an aileron if you let go. The aircraft will then role towards the lifting aileron and will continue to roll since it will remain up.
The common solution is then to squeeze the aileron of the non-heavy wing. This causes its aileron to produce less lift. Its complicated as to why but if you want to understand, and like maths, read up about the Kutta Condition.
I recently had all these problems and currently have a bit of wood to bias first the rudder and then half a coffee stirer stick to bias the aileron. I havnt done the squeeze yet. If you want to see pictures go here. About half way down. You will find links to VANS article and an explanation of the Kutta condition.
OK, that makes the picture a bit clearer. I would suspect the aileron misalignment to have something to do with it. You want the ailerons and flaps to all be aligned perfectly before you start making other adjustments, like squeezing an aileron. You might need to replace one of the aileron hinge brackets. You can order them from Van's without the mounting holes pre-drilled, so that you can measure and drill the holes offset by the amount of the existing error.
Van's has an article on how to diagnose and deal with heavy wing conditions.
http://www.vansaircraft.com/pdf/Wing_Heavy.pdf
Van's has an article on how to diagnose and deal with heavy wing conditions.
http://www.vansaircraft.com/pdf/Wing_Heavy.pdf
L.Adamson
Well Known Member
I was duct taping on your coffee stir stick (actually a piece of tapered R/C balsa) when I noticed that the aileron was a bit thicker on it's trailing edge than the other aileron. This would be the aileron that was suppose to get the squeeze, so that's what I did. I gently squeezed about half, and the ailerons are perfect now.
As in the original post, my ailerons were very level when in trim, or holding the stick. The pressure to hold them level was actually very light, and I didn't even notice it on the first (short) test flight.
In my case, the right wing was heavy enough, that the servo operated tab (1* 6"/ old RV style trim) wasn't quite enough to hold the wings level without a slight bit of stick assist. The left aileron got the squeeze.
L.Adamson --- RV6A
P.S. --- my ailerons and flaps and tips, are lined up perfectly to the wing. No offset problems here..
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Well I spent most of the afternoon looking over the wings yesterday. I ended up slotting the out board hinge on the right aileron to lower it about 1/16 of an inch to make it even with the trailing edge. When I reinstalled the wing tip it came out crooked, trailing edge down more than the aileron. A closer examination of the left wing tip showed it was up the same amount that the right was down. So I taped a triangle wedge 3/4 x 3/8 x 9 on the bottom of the left tip. It made no change. The faster you go the worse it gets. So far it isn't much fun to fly. I think I will put the wedge on the aileron tommorow and try it. Your suggestions and thoughts are appreciated. Hudgin
Check out this thread
http://www.vansairforce.com/community/showthread.php?t=34298&highlight=heavy+wing
Make sure your ailerons are flat when checked with a straight edge as shown in post #3.
Your orig post said...The ailerons are straight it flight and so is the stick but if you let go of the stick it SNAPS to the left stop.
If this is true "snaps to the left stop"...you mean full aileron deflection to the stop with a hard roll to the left?
If this is the case, in my opinion you have a serious flight control problem that needs far more than a trim tab applied to the aileron.
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Steve Sampson
Well Known Member
You say you put the wedge on the tip. If you mean that, you got the result I would expect. i.e. Nothing detectable.
I think when you put it on the aileron, you will find a whole lot changes. Play with it to convince yourself perhaps, but you really do need to sort other misalignements first, and also have it cruising with the ball centered. Good luck!
The ball is in the center and the gear fairings are not installed yet. I didn't want to put them on yet so I could tell if they made the plane fly crooked. My tech counsler just called and said to quit messing around and squeeze the right aileron. He's built and counseled a few of these RV's, so I guess I had better listen to him. Right now it just doesn't make sense. It also doesn't make sense that putting a trim on the tip doesn't change any thing. Shouldn,t they be straight? DH
L.Adamson
Well Known Member
I'm just curious about the word "snap". Is the stick pressure to keep the aircraft level, rather light; like mine was? And if I read everything correctly, I'm assuming that your ailerons are level when in level flight. In other words, the ailerons are not correcting wings with un-even amounts of incidence angle. Is the word "snap" just a bit over done, as I'm envisioning snaps rolls in a Pitts...
In my case, the ailerons were simply "flying" at slightly different angles due to the trailing edge radius. This was causing a roll tendency that was beyond a servo operated trim tab of about 1" * 6".
I could have made the trim tab larger; put offset fixed tabs on both ailerons; a wedge under the left aileron............or the simple squeeze of the slightly fatter aileron, which I did. It has worked perfectly! The main, and important thing, is that the incidence angle of my wings are the same, and all flight surfaces are even with each other.
And BTW, I have my wheel pants and front fairing installed, but not the main fairings. If they were to somehow offset my "heavy right wing", then they'd have to also be out of alignment with the "air stream", wouldn't they? They would essentially be trim tabs, that are also creating additional drag.
One more thing, as previously mentioned, a small wedge on a moveable surface has a lot more force, than when placed on a fixed wing tip.
L.Adamson
I used the word "snap" because unlike other planes I've flown with wing heavy issues where the ailerons move slowly and just a small distance in this case the ailerons moved to and hit the stop the instance the stick was released and of course the plane rolled very quickly. In my past experiances when you have wing heaviness the ailerons are not level to keep the wings level. They have been level on the RV. I would guess the pressure to hold the alierons level was about 2-3 lbs. After squeezing the ailerons today about half of the travel and pressure is gone. And so is the speed at which it moves. There are still "puffs"(?) between the ribs.
As for the wheel and strut fairings I agree with you totaly, that is why I took them off for the inital test flights. After I get the aileron situation fixed then I will put them back on and see if they are acting like "little trim tabs."
How close can you squeez the trailing edge radius before you deform them or crack them? I think I might be on the wrong track by trying to get rid of the puffs between the ribs.
The wing incidince is within a couple of tenths of a degree of each other with the left wing being lower. The flaps measuring at the trailing edge radius are level with the ailerons and are set using the straight edge and holes in the ribs as the guide. I think I should have used a bubble level.
DH
As for the wheel and strut fairings I agree with you totaly, that is why I took them off for the inital test flights. After I get the aileron situation fixed then I will put them back on and see if they are acting like "little trim tabs."
How close can you squeez the trailing edge radius before you deform them or crack them? I think I might be on the wrong track by trying to get rid of the puffs between the ribs.
The wing incidince is within a couple of tenths of a degree of each other with the left wing being lower. The flaps measuring at the trailing edge radius are level with the ailerons and are set using the straight edge and holes in the ribs as the guide. I think I should have used a bubble level.
DH
I would revisit the aileron height alignment. Take a straight edge and lay it along the ribs on the LOWER wing surface to verify that the ailerons are flush with the wing. A small discrepancy CAN cause a significant effect, especially if it's on the outboard end. This sounds like much more than a simple heavy wing/aileron squeeze thing to me.
Well we finally got this part of the airplane fixed. Got the aileron squeezed and it doesint crank over to the left or right any more. But it would go one way or the other and not rlight itself. We put an electric airleron trim in and now it flies hands off and stays there. When it hits a bump now it rights it self. What a pleasure to fly! I can look at the engine instruments and it is still right side up.
Steve Sampson
Well Known Member
DH, how did you organise the squeezing of the ailerons. I still need to do it a little more but am afraid of cosmetic damage. While your experience is still fresh I would be interested to know.
Also, you say:
What are you crediting that to? The aileron squeezing or the presence of the aileron trim or.....?
My ailerons are close to neutral. In many ways I like it but I am interested in your comment.
Also, you say:
What are you crediting that to? The aileron squeezing or the presence of the aileron trim or.....?
My ailerons are close to neutral. In many ways I like it but I am interested in your comment.
Made a template drawing using the edge of the aileron as a pattern and compared it with the other aileron. They were the same so the drawing was transfered to a thin piece of wood and that was used as a gauge to squeeze the trailing edge. We used the vise grip sheet metal pliers with larger pieces of wood between the jaws and the skin to spread out the squeezed area and so as to not leave the imprint of the pliers. It was done very little at a time about a 1/4 inch forward of the trailing edge. We had to move it closer to the trailing edge to get it right and ended up squeezing it more than the template. The template was still useful though cause it gave us a gauge to keep the aileron symetrical. I am not real pleased with the way it came out because that aileron has a concaved look to it compared to the other aileron. It is squeezed thinner than the other one but that is what it took to get the airplane to fly level.
Level means hands off for about 10 seconds or what ever the wind currents will allow. Till the trim kit was installed we were always correcting wing level either way. That is how we knew we were done. We did very little at a time so we wouldn't have to bend the other aileron. The trim kit comes with springs in it and seems to bring the wings back to where they were before they were disturbed. The RV doesn't have as much dihedral as a Cherokee and rightfully so but now it is as stable as one. (figuritively speaking) Hope this helps. DH
Level means hands off for about 10 seconds or what ever the wind currents will allow. Till the trim kit was installed we were always correcting wing level either way. That is how we knew we were done. We did very little at a time so we wouldn't have to bend the other aileron. The trim kit comes with springs in it and seems to bring the wings back to where they were before they were disturbed. The RV doesn't have as much dihedral as a Cherokee and rightfully so but now it is as stable as one. (figuritively speaking) Hope this helps. DH
Kutta Condition
I have been flying my RV-7A for over 3 years and 300 hours with a left heavy wing.
Today, after many many hours of analyzing the problem and reading many different opinions, I finally decided to squeeze the trailing edge of the aileron on the ?LIGHT? wing. I did this by hand ? It took about 3 minutes, then I took it for a test flight.
Guess what ? It worked ? No more heavy wing !!
Prior to squeezing the aileron, I tested the stick force using a fish scale and safety wire tied to the stick (no aileron trim ? ie neutral trim). When cruising at 160KTAS
(152 KIAS) I needed to hold 4.5 lbs tension to the right to achieve level flight. When in cruise at 118 KTAS (113 KIAS) I needed to hold 1.5 lbs to the right. When flying slow at 70 kts I didn?t need any tension on the fish scale.
I agonized over; aileron hinge, wing tips, rigging of the controls, rudder alignment, etc, etc. Until reading up on ?Kutta condition? I guess I didn?t think this was my problem. But it definitely was & a quick 3 minute squeezing of the ?LIGHT? wing?s Aileron?s TE did the trick.
Now I am a believer - With a level RV.
I have been flying my RV-7A for over 3 years and 300 hours with a left heavy wing.
Today, after many many hours of analyzing the problem and reading many different opinions, I finally decided to squeeze the trailing edge of the aileron on the ?LIGHT? wing. I did this by hand ? It took about 3 minutes, then I took it for a test flight.
Guess what ? It worked ? No more heavy wing !!
Prior to squeezing the aileron, I tested the stick force using a fish scale and safety wire tied to the stick (no aileron trim ? ie neutral trim). When cruising at 160KTAS
(152 KIAS) I needed to hold 4.5 lbs tension to the right to achieve level flight. When in cruise at 118 KTAS (113 KIAS) I needed to hold 1.5 lbs to the right. When flying slow at 70 kts I didn?t need any tension on the fish scale.
I agonized over; aileron hinge, wing tips, rigging of the controls, rudder alignment, etc, etc. Until reading up on ?Kutta condition? I guess I didn?t think this was my problem. But it definitely was & a quick 3 minute squeezing of the ?LIGHT? wing?s Aileron?s TE did the trick.
Now I am a believer - With a level RV
.
L.Adamson
Well Known Member
Amazing isn't it!!!
My heavy wing couldn't be leveled with full aileron trim. And my trim is actually one of those servo controlled tabs that sit's outboard on the aileron.
The force to stay level was rather light, so I put up with it for a few months.
Was going to tape a temporary wedge on the bottom of the opposite aileron when I noticed that the trailing edge was slightly thicker than that of the heavy wing. Took out my hand seamers, slightly flattened a foot or so, and it came out perfect. It didn't effect my paint job either. I now have a centered aileron trim that can easily move in either direction to account for fuel, passenger, etc. (Note: the 6's ailerons are folded aluminum for the trailing edge. I know that some models differ.)
L.Adamson -- RV6A
Hudgin - Thank You; The other thing I noticed is my ailerons take more force (or so if feels) before they were very "loose" feeling - now it feels stable at higher speeds
Hi Adamson - Yes I was very surprised it actually worked. My Ailerons were quick build & they looked like they were the same radius at the TE. Tonight I am very happy & can't believe I put up with it for over 3 years - for something that was really that easy & quick to fix (looking for a tool in my hanger but didn't find one so - I used my bare hands). It was this Thread that convinced me to try it - Thanks Guys!
The way I see it there will always be some degree of heavy left wing in the cruise even in a perfectly built aircraft due to the torque effect from the engine. Now I know that the VS is offset to allow for torque effect but I presume this is mainly to keep the ball center rather than lifting up the left wing. I have always needed some amount of right trim (usually small) in cruise and have assumed that I have a slightly heavy left wing. However in a glide with the engine at idle I find I need to move the trim to at least neutral or maybe even a small amount of left trim for hands free level flight, so can I conclude that I do not have a heavy left wing and that the need for right trim in the cruise is due to torque effect rather than a slight rigging problem?
Fin
9A
Fin
9A
Hi Fin
I am not an expert, but I have never flown any plane that didn't need some trim (Ail, Elev, or Rud) under various flight conditions. With my heavy left wing problem - with neutral ail trim - my left aileron (trailing edge) would always want to lift up about an 1". This would create a bank & thus the "heavy left wing". The faster I went, the greater the "right" stick force needed to keep the wings level. From everything I researched, this is caused by "Kutta Condition". I suppose engine torque could be a factor, but not to the degree I had (If I got up to 160kts & powered down my plane would still roll significantly to the left). I will set up my plane for neutral trim under my most common flight condition "Cruise". All I can tell you is squeezing the "LIGHT" wing's aileron Trailing edge slightly fixed my problem. If I am not mistaken a 9 model doesn't have a radius TE on the Ail & this squeezing isn't an option
It is really aggravationg to have an out of trim condition.
...in any airplane. The first priority of business after the first flight, is, in my opinion, straightening out the airplane. My -10 had two years and 220 hours of flight and the ball was 3/4 out with hands and feet off when it was delivered to me.
I took an 8" piece of wood, 1 1/4" wide, that I cut at a 10 degree angle on my table saw and 3 flights trimming that piece until straight, no rudder needed ,flight. You can do the same thing on the underside of a -9's aileron where no one will notice it, or bend the trailing edge near the tip. Duct tape the tab in place while you take a short flight. Mine was corrected in less than an hour total, so I siliconed it permanently.
Best,
...in any airplane. The first priority of business after the first flight, is, in my opinion, straightening out the airplane. My -10 had two years and 220 hours of flight and the ball was 3/4 out with hands and feet off when it was delivered to me.
I took an 8" piece of wood, 1 1/4" wide, that I cut at a 10 degree angle on my table saw and 3 flights trimming that piece until straight, no rudder needed ,flight. You can do the same thing on the underside of a -9's aileron where no one will notice it, or bend the trailing edge near the tip. Duct tape the tab in place while you take a short flight. Mine was corrected in less than an hour total, so I siliconed it permanently.
Best,
A balanced side by side will have a "heay wing"
I just have to add for the sake of reference that all side by sides will have a "heavy left wing" unless you put an equal weight to the pilots weight in the passenger seat.
That is not a "heavy wing" just an out of trimmed airplane when flying solo. You have to decide if that is acceptable or if you want to "rig" or "trim" your airplane primarily for solo flight.
Even though I fly primarily solo, I have left my airplane alone as I prefer to have it balanced rather than trying to overcome my weight with rigging or trim for solo flight. That is a personal preference. I fly off the left tank first to lessen the stick forces, which are not severe at all.
So, make sure you know what you have before you start messing with it. Put a passenger of equal wieght in and go fly. Once you know your airplane is straight, then you have a reference and troubleshooting the problem should be easier.
I just have to add for the sake of reference that all side by sides will have a "heavy left wing" unless you put an equal weight to the pilots weight in the passenger seat.
That is not a "heavy wing" just an out of trimmed airplane when flying solo. You have to decide if that is acceptable or if you want to "rig" or "trim" your airplane primarily for solo flight.
Even though I fly primarily solo, I have left my airplane alone as I prefer to have it balanced rather than trying to overcome my weight with rigging or trim for solo flight. That is a personal preference. I fly off the left tank first to lessen the stick forces, which are not severe at all.
So, make sure you know what you have before you start messing with it. Put a passenger of equal wieght in and go fly. Once you know your airplane is straight, then you have a reference and troubleshooting the problem should be easier.
mosquito
Well Known Member
Unsqueezing an aileron?
Hi,
I've purchased a -6 that has a heavy right wing. The manual aileron trim in the left-most position _almost_ compensates, but not quite. Upon careful examination, I've discovered that the right wing's aileron has been squeezed along it's full length, while the left has not. Unfortunately, the builder is deceased, so I'm on my own for an explanation. I'd love to hear any thoughts on this... should I try to unsqueeze the right aileron somehow, as a starting point? If so, any recommendations on how to accomplish that? I recall seeing a post that described placing a 2x4 against the trailing edge and gently whacking it until the radius increased, but I can't seem to find it.
Thanks!
-jon
Hi,
I've purchased a -6 that has a heavy right wing. The manual aileron trim in the left-most position _almost_ compensates, but not quite. Upon careful examination, I've discovered that the right wing's aileron has been squeezed along it's full length, while the left has not. Unfortunately, the builder is deceased, so I'm on my own for an explanation. I'd love to hear any thoughts on this... should I try to unsqueeze the right aileron somehow, as a starting point? If so, any recommendations on how to accomplish that? I recall seeing a post that described placing a 2x4 against the trailing edge and gently whacking it until the radius increased, but I can't seem to find it.
Thanks!
-jon
Yep, that's the way to do it. HOWEVER......
I don't really recommend trying it. It can destroy the aileron skin quite easily. The preferred method would be to squeeze the left aileron to compensate.
I don't really recommend trying it. It can destroy the aileron skin quite easily. The preferred method would be to squeeze the left aileron to compensate.
Hey guys,
I know this is an old thread,
I ran across it on a google search.
I have the exact problem as the OP.
Release the stick and it snaps to the left, approx 5lbs of force to hold it centered.
The fix is pinching the trailing edge of the light aileron.
My question is why pinch the light aileron ??
Im thinking if the stick snaps to the left the left aileron (airfoil) is producing too much lift and it snaps up ??
In my case and the OP what is happening with the light aileron to make it move down which then the left aileron moves up.
Is there some kind of eddy at the trailng edge that produces a low pressure under the light aileron "pulling" it down ??
Im confused
Thx
Gregg
I know this is an old thread,
I ran across it on a google search.
I have the exact problem as the OP.
Release the stick and it snaps to the left, approx 5lbs of force to hold it centered.
The fix is pinching the trailing edge of the light aileron.
My question is why pinch the light aileron ??
Im thinking if the stick snaps to the left the left aileron (airfoil) is producing too much lift and it snaps up ??
In my case and the OP what is happening with the light aileron to make it move down which then the left aileron moves up.
Is there some kind of eddy at the trailng edge that produces a low pressure under the light aileron "pulling" it down ??
Im confused
Thx
Gregg
The best place to start is reading through some of the other threads linked to from this one, and reading the chapter in section 5 of the construction manual.
Describing what the cause and remedy is would involve far more than a couple of sentences…… and all the needed info is available in those other threads.
There are a number of threads on this issue.
Another heavy wing thread...
My RV8 (bought not built) has a slightly heavy right wing- (about 3 gallons worth which Vans considers minor). But there's a few other factors at play- the right wing, everything lines up nicely- Flap is UP (measured by straightedge on bottom of wing), aileron clamped to flap, aileron aligned...
vansairforce.net
I was trying to install new wingtips and discovered that I couldn’t follow the Vans directions because the ailerons were intentionally mis-rigged due to a heavy wing situation.
Long story short, in mapping out the wings, I figured out that the left flap wasn’t made the same as the right and was hanging 1/4” lower.
You can DM me if you like but the guy you really want to talk to is Carl Froehlich here on VAF.
Hey guys,
Thank you for the replies.
I spent the weekend researching as suggested.
I still don't understand is what is happening to the light aileron ??
Releasing the stick it snaps to the left which means the left aileron is moving up and the right aileron is moving down.
What is making this happen ??
If the fix is pinching the trailing edge on the light aileron then what is acting on the light aileron ??
It has to be low pressure underneath "pulling" it down or high pressure on top "pushing" it down.
I want to understand the physics of this.
Thoughts ??
Thank you for the replies.
I spent the weekend researching as suggested.
I still don't understand is what is happening to the light aileron ??
Releasing the stick it snaps to the left which means the left aileron is moving up and the right aileron is moving down.
What is making this happen ??
If the fix is pinching the trailing edge on the light aileron then what is acting on the light aileron ??
It has to be low pressure underneath "pulling" it down or high pressure on top "pushing" it down.
I want to understand the physics of this.
Thoughts ??
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Mine had a heavy left. If I left go, it would roll left. Not what I would call a snap, but required attention.
Before pinching anything. Read the threads and Vans document carefully. Fly the airplane with full tanks on the left tank. Does it ever get neutral? If so how much gas. Mine took about 10 gallons. 60lbs.
Two other 7s on my row had a similar heavy wing. Both right. Mine was left.
We examined the airplane and both agreed the left aileron was maybe 1/16" higher at the hinge side. It was visible looking fore/aft across the chord. They had the same issue on the right and notched the hinge brackets per Vans Service Letter. So I notched the left. She flies straight now.
Before pinching anything. Read the threads and Vans document carefully. Fly the airplane with full tanks on the left tank. Does it ever get neutral? If so how much gas. Mine took about 10 gallons. 60lbs.
Two other 7s on my row had a similar heavy wing. Both right. Mine was left.
We examined the airplane and both agreed the left aileron was maybe 1/16" higher at the hinge side. It was visible looking fore/aft across the chord. They had the same issue on the right and notched the hinge brackets per Vans Service Letter. So I notched the left. She flies straight now.
A lot has been written in the forums on this in the past, but I guess in your reading you didn’t find it.
The aileron part of the control system is a closed loop system.
That means the ailerons, though each doing specific work on individual wings, are tied together and cause a reaction to each other.
When everything is normal, that reaction is equal and balanced so that the aileron will stay in the neutral position if there is no outside control influence through the control stick.
If there is something that is affecting the reaction of one aileron in flight that makes its reaction force into the system different from the other one, that balance in the system has been upset and the one that’s exerting the most force will cause a displacement of the system.
One of the extremely common causes of this is that the two ailerons are not exactly the same shape on their entire spans.
If the trailing edge shape is incorrect, it can make an aileron act as though it is shorter cord dimensionally than it really really is. This is the result of a flow separation that occurs forward of the trailing edge, because of a pucker/incorrect shape.
As a result, the aileron that acts bigger will have more lifting force against the bottom of it, which will allow it to displace both ailerons from the neutral position.
There are numerous different things that can have an influence on the imbalance, but the very first one you should investigate, as I already mentioned, is the proper shape of the trailing edge of the ailerons.
The wrong thing to do in this situation is just jump to adjusting one based on the standard process, by squeezing the trailing edge, because the opposite one may already be over squeezed. Doing so is just making your airplane have two ailerons that are totally the wrong shape which will induce other issues.
None of us would just guess at having the correct airfoil shape on the wing, so we shouldn’t do that with the ailerons either because their shape is part of the wing airfoil.
So go to section 5 of the construction manual, you can download it from Van‘s website in the support section after selecting your airplane model. If you don’t already have it, and use the info in that section to inspect the shape of both of your ailerons (you should probably do the elevators and Rudder as well)
If they both check out as being what they should be ( extremely unlikely), then you can move onto other remedies for solving the problem.
Like I already said, I would use caution in just making an adjustment as a quick fix to solve your issue without knowing what the exact issue is.
The aileron opposite of the one you would squeeze, may already be over squeezed / incorrect shape in the opposite direction.
If you over squeeze the other layer on, you may get them balanced, but you now have ailerons that will feel a lot heavier than an RV that flies properly.
That is the reason I directed you to the check process in section 5, and why Vans Aircraft took the time to put it in the manual.
I think that applying a fix without a set of detailed measurements and mapping is not a great idea.
Determining the Root cause vs throwing things at a symptom.
The builder of my aircraft ended up mis-rigging the ailerons to make the heavy wing ‘less bad’ all because there was an issue when a flap was made that caused that flap to hang down 1/4” lower than the other side.
With the aircraft leveled for W&B. Map the leading edge of each wing at the I/B & O/B points with a plumb bob. Do all 4 points line up in a straight line when you stretch a string line across the points?
Get out your digital inclinometer and verify the angle of the upper surface of the wing every 2 feet on both wings. Was a twist built into the wing?
I don’t remember the exact procedure but you will need to map/measure both flaps. I used masking tape, a sharpie, a block of wood, a digital caliper, and a 4’ straight to measure the drop every 3” I/B to O/B, and FWD edge to Trailing edge.
If you do the same thing with the ailerons you’ll need to immobilize the control stick at the neutral position.
Masking tape is great for locating where you need to take measurements and is a handy place to make notes.
SixSigma: if you can measure it you can change it. If you can't measure it, you can't improve it.
DMAIC — Define, Measure, Analyze, Improve, Control.
Assumptions and gut feelings is not a good troubleshooting tool when removing or bending metal is a one way street. Unless you like doing recreational maintenance.
